This invention relates to a novel pyridazinone derivative or a salt thereof which is useful for a cardiac stimulant.
Various cardiac stimulants, which effect a direct enhancement of the cardiac contraction, have been available in the treatment of cardiac insufficiency. However, these cardiac stimulants may have some defects such as follows: (1) their safety margin is extremely small; (2) they may cause arrhythmia; (3) their cardiac stimulating activity is transient; and (4) they may not be suitable for oral administration.
A primary object of the present invention is to provide a novel cardiac compound having a high and sustained activity.